Field of the Invention
The present invention relates to extruded polymer foam containing low bromine content and a process for preparing such extruded foam.
Description of Related Art
Extruded polymeric foam typically contains brominated flame retardants in order to achieve an acceptable level of flame resistance. A well known standard for flame resistance is the German B2 fire test according to DIN 4102. Such a flame resistance is particularly desirable for thermally insulating polymeric foams for use in building and construction applications. Brominated flame retardants such as hexabromocyclododecane (HBCD) have increasing restrictions on their use in extruded polymeric foam due to a negative environmental stigma associated with them. Therefore, it is desirable to minimize the level of brominated flame retardants in extruded foam to optimize the perceived environmentally friendly character of the foam.
European patent (EP) 0863175B1 describes a thermally insulated extruded polymeric foam that comprises graphite and a brominated flame retardant. The polymer foam reportedly only passes the German B2 fire test provided the concentration of bromine flame retardant compounds is more than two weight-percent (wt %) or is used in combination with 0.1 to 0.5 wt % of a C—C or O—O labile organic compound. Moreover, the brominated flame retardant must contain at least 70 wt % bromide. Therefore, the teachings of EP0863175B1 indicate that more than 1.4 wt % bromide is require to pass the German B2 fire test unless 0.1 to 0.5 wt % of C—C or O—O labile organic compounds are present.
It is desirable to achieve thermally insulating extruded polymeric foam that passes the German B2 fire tests in without requiring 0.1 to 0.5 wt % of C—C or O—O labile organic compounds and without requiring more than 1.4 wt % bromide.